A session border controller (SBC) is a piece of network equipment or a collection of functions that control real-time session traffic at the signaling, call-control, and packet layers as they cross a notional packet-to-packet network border between networks or between network segments. An SBC may consolidate interconnect points, provide and enforce QoS metrics, interwork between protocols, and provide a more secure connection for intersite calling. SBCs may address the inability of real-time session traffic to cross network address translation (NAT) device or firewall boundaries.
Multimedia content, such as video on demand (VOD) may be requested and controlled using real-time stream protocol (RTSP) as a signaling protocol. The content may be delivered using real-time transport protocol (RTP), a protocol for the transport of real-time data, such as audio and video. Some user may wish to use session initiation protocol (SIP) as a signaling protocol to request and control multimedia content that may be available from content providers that use RTSP.